Does a Magnetic Resonance Imaging (MRI) of the lumbar spine detect Sacroiliac (SI) joint pathology?

From the Guidelines

MRI of the lumbar spine is not the optimal imaging modality for detecting SI joint pathology, and a dedicated SI joint MRI is recommended for comprehensive assessment. While a standard lumbar spine MRI may capture the superior portion of the SI joints, it often does not fully image these joints or use sequences optimized for SI joint evaluation 1. For patients with suspected axial spondyloarthritis, MRI of the sacroiliac joints and spine is associated with improved diagnostic confidence, but there is heterogeneity in clinical practice regarding the use of MRI to evaluate the sacroiliac joints and/or spine in these patients 1.

Some key points to consider:

• A dedicated SI joint MRI uses specific protocols with thin slices, appropriate field of view, and sequences sensitive to inflammation and structural damage 1.
• Conditions like sacroiliitis, ankylosing spondylitis, and other inflammatory arthropathies affecting the SI joints may be missed on routine lumbar spine imaging 1.
• If SI joint pathology is suspected based on clinical presentation, it's best to specifically request SI joint imaging 1.
• CT scans can also be useful for evaluating structural changes in the SI joints, while MRI is superior for detecting active inflammation, bone marrow edema, and soft tissue abnormalities 1.
• The decision on whether to image the spine as well as the sacroiliac joints could be based on the site of symptoms, and imaging the spine in the clinical region of interest is beneficial in the setting of referable symptoms 1.

In terms of diagnostic utility, the presence of two or more corner inflammatory lesions on spine MRI has a sensitivity of 69% and specificity of 94% for ankylosing spondylitis, and the presence of multiple fatty corner lesions in the spine has a high specificity of 98% for axial spondyloarthritis 1. However, the findings on spine MRI should be interpreted alongside sacroiliac joint MRI to ensure the highest diagnostic utility 1.

From the Research

MRI Lumbar Spine and SI Joint Pathology

• The study 2 suggests that MRI lumbar spine scans may not be effective in catching SI joint pathology, as it was found in only 0.02% of patients, and the authors propose that the SIJ should be imaged only if significant clinical findings are demonstrated.
• However, other studies 3, 4 highlight the importance of considering SI joint dysfunction as a potential cause of low back pain, and the use of MRI in diagnosing and evaluating SIJ dysfunction.
• The study 5 found that MRI scores of inflammation on the SIJ were significantly decreased in patients with axial spondyloarthritis treated with TNF alpha inhibitors, but the correlation between MRI scores and clinical and biological data was heterogeneous.
• The study 6 discusses the challenges in diagnosing sacroiliitis using MRI, as the appearance of sacroiliac joint MRIs can resemble other conditions, and highlights the need for further research to distinguish between sacroiliitis and differential diagnoses.

Diagnostic Challenges

• The diagnosis of SIJ dysfunction is difficult, with high intra and inter-observer variability in clinical provocative tests 2.
• The use of physical maneuvers and image-guided anesthetic injection can aid in diagnosis, but improved diagnostic methods are critical to properly identify patients suffering from SIJ dysfunction 4.
• The study 6 highlights the need for further research to develop optimal MRI approaches to distinguish between sacroiliitis and differential diagnoses.

Treatment Options

• Non-operative treatment options, such as conservative management, radiofrequency treatment, nerve blocks, and articular injections, are considered first-line for SIJ dysfunction due to high surgical complication rates 4.
• Surgical management, including open and percutaneous approaches, may be considered for patients who do not respond to non-operative treatment 4.